KID 10 (yingu) and the Posterior Knee

KID 10 (yingu) is a very interesting point in relationship to the knee and knee injury and pain. It contains some fascinating anatomy that might not be apparent on first glance. 

Peter Deadman, in A Manual of Acupuncture, describes the location thus: “At the medial end of the popliteal crease, between the semitendinosus and semimebranosus tendons.” Claudia Focks, author of Atlas of Acupuncture, has a similar description: “At the medial end of the popliteal crease, between the tendons of the semimembranosus and semitendinosus muscles, on the level of the knee joint space.”

I find these descriptions a bit confusing, as they don't completely match what we find in palpation. In a way, it might be more accurate to say that KID 10 is between the semimembranosus and another part of the semimembranosus. If you press into the space between the semitendinosus and the semimebranosus tendon, you might be able to feel a very thin, but palpable band. This band will definitely contract when the knee is flexed, verifying that it is a hamstring.

In this illustration, the semitendinosus tendon has been
removed. It would be lateral (to the right of)
semimebranosus (SM). I think KID 10 is about
where the label for 'Coronary attachment' is in
the above illustration.

What hamstring muscle is between the semimembranosus and semitendinosus tendon, you might ask? Look at most anatomy books and you won't find one. The answer is that this band is a fibrous expansion of the semimembranosus tendon which blends into the oblique popliteal ligament (a major structure of the posterior joint capsule). I think KID 10 is between the main body of the semimembranosus and this lateral expansion. If you advance into this space, you will affect the fascia of the fibrous expansions of the semimembranosus.

Press slowly and gently into this space and you will frequently elicit a referral deep into the knee joint and into the medial tibia. Needling into this would contact this proprioceptive rich fascia which blends with the posterior capsule of the knee. These expansions also have connections to the medial meniscus and the medial collateral ligament (see 'anterior arm' in the image to the left).

If you press or needle lateral to this expansion, in other words, between it and the semitendinosus, you miss this fascia altogether. 

This is a somewhat challenging area to palpate. When palpating, stay very close to the lateral border of the main tendon of the semimembranosus and you will slide between it and this fascial expansion. Having the knee flexed helps with palpation.

In addition to KID 10, and when presented with medial knee pain and/or problems with the posterior knee capsule, you might consider treating the motor points of two muscles of the Kidney sinew channel: semimembranosus and popliteus. As can be seen in the image above, these muscles are very connected to this important fascia that stabilizes and supports the posterior and medial knee. Obviously, there is a lot more assessment that would be required to build a treatment plan, but these suggestions would frequently be applicable for MCL injury, medial meniscus injury, weakness of the posterior joint capsule, and medial knee pain referred from semimembranosus.

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